1.1 Field of the Invention
The present invention relates generally to chemical distribution systems, and more particularly to chemical dispensing apparatus. Still more particularly, the present invention is a chemical dispense head assembly designed to maximize safety, chemical throughput, and ease-of-use.
1.2 Description of the Background Art
In many chemical distribution systems, a drum or tank serves as a chemical source or reservoir. A dispense head assembly that mounts to the drum, such as that described in U.S. Pat. No. 5,108,015, selectively controls fluid flow between the drum and chemical distribution piping. Semiconductor manufacturing environments provide well-known examples in which chemical distribution is accomplished in this manner.
A dispense head assembly design should satisfy several requirements. A first requirement is the maximization of chemical throughput, which may be especially critical in manufacturing environments. Prior art dispense head assembly designs, however, include flowpath obstructions and/or small-diameter flowpaths that undesirably limit the chemical flow rate.
A second requirement is simple, rapid coupling to and decoupling from the drum. Unfortunately, typical prior art dispense head assemblies must be completely screwed into or screwed out of the drum each time the dispense head assembly is coupled to or decoupled from the drum, respectively.
Another requirement is the maximization of safety, particularly when dealing with hazardous chemicals. This in turn requires that the dispense head assembly be key-coded, plus leakproof when coupled to the drum, as well as essentially dripless when decoupled from the drum. Unfortunately, the safety performance of some prior art dispense head assemblies has been known to degrade over time.
What is needed is a dispense head assembly that couples to a drum in a simple manner and safely provides high fluid flow rates through a large, essentially unobstructed flowpath.